The present invention relates to a method for measuring the light absorption coefficient of a light scattering material and the device of the same and further it relates to a diagnostic imaging device (optical CT imaging device) utilizing the method.
For the observation of a tomograph image in a human body, an X-ray CT method is widely used. Since a state inside a human body can be known without performing an operation for an observation object (human body) by using an X-ray CT device, it is widely used for diagnostic purposes. On the other hand, a problem of lesion by radiation of X-rays on a human body cannot be neglected. The development of an optical CT imaging device in which rays of light is used in place of X-rays is suggested as a method for solving the problem. In order to realize an optical CT device, it is necessary to measure the information inside a human body with rays of light. There are papers as shown below as the examples in which the measurement of the information inside a human body is attempted with rays of light.
In 1977, a measurement of a physiological change which occurred in a human head based on the change in the transmitted light intensity by irradiating the head of an adult with infrared rays was attempted by F. F. Jobsis. This was the first attempt on the measurement of change in light absorption quantity corresponding to the physiological change inside a head, and the details are described in a Japanese Kokai No. 115232/82. In the gazette, there is a comment on the constitution of an optical CT imaging device utilizing the above-mentioned measurement method, but the idea is based on a simple idea of substituting a light beam for X-rays in an X-ray CT imaging device.
Another measurement device for measuring the information inside a human body with a light beam is shown in a Japanese Kokai No. 163634/90. In the device, a light-scattering substance is irradiated by a light beam, and the reflected light which comes in the vicinity of the light incident point is detected for the measurement of the information inside a human body.
There is a further paper than the above described papers, reporting that an optical CT image is obtained by measuring light absorption characteristics of a light-scattering substance with a faint light measurement method called a light heterodyne method (Toida et al, "Measurement of a Faint Signal Light Buried in Scattered Light", BME Journal, Vol. 4 (1990), pp 1223). In a case where a transmitted light through a light-scattering substance is measured by a light heterodyne method, the intensity of the transmitted light becomes very weak, so that this method cannot be applied to a thick specimen.